1. Field of the Invention
The present invention generally relates to computing or storage racks (e.g., cabinets, libraries) for holding computing devices or field replaceable units (FRUs) such as servers, tape drives, other electronic equipment, and the like and, more particularly, to a system that, upon removal of a FRU from a rack, automatically limits unintended airflow (e.g., hot airflow) recirculation through the empty space or bay where the FRU was installed in the rack to thereby improve equipment reliability, simplify service of individual FRUs, and the like.
2. Relevant Background
Information technology (IT) racks are standardized frames that are designed to hold a plurality of computing devices or related equipment (e.g., rack-mounted servers, power distribution units or backup devices, hard drives, and/or other types of FRUs) in, for instance, a stacked or side by side manner. Generally, rack systems include a mechanical framework made up of a number of vertical support members (e.g., posts, Radio Electronics Television Manufacturers Association (“RETMA”) rails) extending upward from a floor or other platform and defining a storage space therewithin into which FRUs may be inserted. Typically, the vertical support members define a plurality of “bays,” where each bay is configured to receive a corresponding FRU. Each bay may have a standardized height in one or more multiples of a rack unit (U) to correspond with correspondingly sized FRUs. For instance, industry standard rack systems often come in heights of 18 U, 22 U, 36 U, 42 U, and the like. Also, a rack system may be in the form of a 19-inch rack (i.e., the width between the front two vertical members may be 19″), a 23-inch rack, or the like.
It is generally desirable for each FRU to be installed and/or serviced without affecting operation of the other FRUs, and, in many cases, it is desirable for each FRU to be maintained or accessed without disconnecting it from power or communications/network links (e.g., to provide hot swappable and maintainable servers in an enterprise or data center environment). To this end, each FRU may be mounted within a bay of the rack using a rail, slide or rack-mount kit. A rail kit typically includes a pair of outer rail assemblies, each of which is attached to vertical support members of the rack and extends horizontally to define a server mounting location within a bay of the rack. Each outer rail assembly may be mated or otherwise interconnected with a middle rail or middle member of the rail kit. The middle rail often will be supported within an inner channel or groove of the outer rail assembly and the middle rail may be positioned by sliding within the outer rail assembly between refracted and extended positions. In the extended position, the middle rails typically extend outward from the ends of the outer rail assemblies several inches to a foot or more to allow access to an attached or supported server or other computing device. In the refracted position, the middle rail has its outer end positioned within the outer rail.
To mount a server in the rack, a pair of inner or rack rails is attached to an outer surface of a server (or other computer device) chassis, and each of the inner or rack rails is coupled with or otherwise interconnected to a corresponding one of the middle members or rails. Generally, a server is mounted within the server storage rack by extending out the middle rail, aligning the ends of the both of the inner or rack rails on the server chassis with the ends of the middle rails, and, once proper alignment is achieved on both sides, pushing on the server chassis to cause the inner rails or racks to mate or couple with the middle members or rails (e.g., in a tongue-and-groove manner) as the inner rails slide within channels or grooves of the middle member or rails. Continued pushing then causes the middle member or rail to slide within the outer rail or member from the extended position to the retracted position, which allows any storage rack doors to be closed.
One important consideration to be taken into account when designing and arranging computing/electronic racks that store a plurality of FRUs is airflow management through the racks. Generally, a FRU mounted within a receiving bay of a rack cools itself by drawing in ambient air through an air intake adjacent the front of the FRU via a front of the receiving bay and then exhausting hot air out the back of the FRU via a rear of the receiving bay. Oftentimes, cold air (e.g., from an air conditioning system) can be exhausted from floor vents for uptake by the fronts of the mounted FRUs in an attempt to maintain proper operating temperatures of the FRUs (i.e., to reduce the likelihood of overheating and possible failure). Furthermore, rows of racks can be oriented in a “face-to-face” orientation to reduce the likelihood that the hot air exhausted from the rear of one rack is drawn in through the front of an adjacent rack (which could lead to overheating of FRUs in the adjacent rack).
Despite the above precautionary measures that aim to maintain proper FRU operating temperatures in computing racks, possibilities still exist for hot air exhausted by FRUs of a particular computing rack to be recycled/re-circulated and drawn back into the air intakes of the FRUs of the particular computer rack. For instance, one situation where such exhaust air recycling can occur is when a FRU is removed from a receiving bay of a rack or, in other words, when a particular receiving bay of a rack is empty. In this situation, hot air being exhausted out of the rear of the rack can be drawn back through the empty bay to the front of the rack and eventually into the air intakes of the FRUs that are still mounted in the rack (e.g., particularly, those FRUs adjacent the empty bay). Such air recycling can be caused by, for instance, air pressure differences between the front and rear of the rack (e.g., the high pressure exhaust air attempting to equalize with the low pressure, relatively cool inlet air). In the case of large-scale computing rack deployments (e.g., large corporations having server rooms with hundreds or even thousands of racks), the negative effects owing to such hot exhaust air recycling can be quite dramatic. For instance, the increased energy consumption by server fans attempting to cool off servers within a rack due to hot exhaust air recycling can result in substantial cost and operational issues for the operator of a compute farm or server area, especially when multiplied over hundreds or thousands of racks (some of which may be distributed around the world).
One common technique used in an attempt to counteract the above phenomenon is by mounting one or more “blanking panels” over the front of the empty receiving bays (e.g., empty vertical spaces) of the computing rack. For instance, such blanking panels can range from simple plastic or even cardboard panels that may be placed across the front of the empty bays to more sophisticated arrangements having snap-on retention mechanisms that hold the panel onto the front of the rack. Regardless of the specific design, the fundamental principle of a blanking panel is to limit the recycling of hot exhaust air from the rear of the rack through the empty bay or vertical space to the front of the rack that may otherwise be drawn in by FRUs mounted in the rack and lead to overheating of such FRUs, among other complications.